The present invention provides a process of iodization and fractional distillation of metals, alloys and/or mixtures containing high value metals, including but not limited to, refractory metals in a wide range of weight percentages of such metals as included in various starting materials followed by reduction through use of a reducing agent or thermal decomposition, preferably hydrogen reduction, to recover some or all of the high value metals. In some instances novel forms of the recovered metal values are achieved.
There are known hydrometallurgical and pyrometallurgical methods for processing alloys, containing nickel and cobalt and also containing one or more of tantalum, rhenium, tungsten, molybdenum and/or other refractory metals (superalloys). For example as to hydrometallurgical processing, U.S. Pat. No. 5,776,329 of Krynitz et. al. (Jul. 7, 1998) teaches electrochemical oxidation of such alloys in an organic electrolyte and separation of alloying metals via chemical processing. The process is a complex one. It calls for various organic and inorganic electrolytes such as methanol, ethanol, isopropanol, phenol, lithium chloride, sodium nitrate, cobalt chloride, nickel chloride, ammonium chloride. A published US Patent Application 2009/0255372 by Olbrich et. al. (Oct. 5, 2009) discloses pyrometallurgical processing of a superalloy containing tungsten in a salt melt containing NaOH, Na2SO4 and other sodium containing oxidizers. Sodium tungstate is dissolved in water, thus being separated from the cake. The filter cake is again suspended in water and the metallic, magnetic fractions are separated from the oxide and hydroxide fractions. The hydroxide sludge is sent to a tantalum facility for digestion and recovering of tantalum, while the metal sludge is forwarded to a nickel facility for recovering of heavy metals.
In another example of the prior art, superalloys are processed via electrochemical decomposition of electrodes formed by a superalloy. The polarity of the electrolysis current is reversed with frequency of from 0.005 to 5 Hz (US Published Patent Application 2008/0110767 by Stoller et. al., May 15, 2000). Rhenium is recovered via ion exchange technology.
All prior art processes mentioned above are multi-step. They generate a variety of streams and are costly.
There are known techniques to recover tantalum and niobium via iodization of impure metals. Nishizawa et. al. in U.S. Pat. No. 4,720,300 (Jan. 19, 1988) disclose a process for producing niobium metal, which comprises iodizing niobium metal or niobium chloride containing at least tantalum as an impurity, then thermally decomposing the iodized product. It is practiced in a vacuum and has difficulties obtaining full Ta extraction.
Rosenberg et. al. in U.S. Pat. No. 6,958,257 (Oct. 25, 2005) and U.S. Pat. No. 7,102,229 (Sep. 5, 2006) describe a method for producing tantalum by first iodizing solid tantalum at 500-800° C., then decomposing TaI5(gas) in vacuum. Thermal decomposition of tantalum iodide in vacuum leads to unavoidable losses of tantalum in a form of TaI5.
Scheller et al. in U.S. Pat. No. 3,211,548 (Oct. 12, 1965) disclose production of tantalum or niobium by hydrogen reduction of crude material sources of Ta, Nb and/or Ta, Nb chlorides in a plasma jet and compare it favorably vs. then prior art techniques such as electrolytic and thermite processes. They cite an article “The Plasma Jet” in Scientific American, vol. 197 (2) pp. 80 et. seq. (1957) re carbon reduction in a plasma furnace. An article by Yuri V. Blagoveshchenskiy et al. in the Journal of Rare Metals, vol. 28, Special Issue of October 2009, pp. 646 et seq. describe hydrogen/plasma reduction of tantalum and niobium chlorides for realization of nanoscale powders (5 to 100 nanometers) with a raw material evaporated into a gas stream mixed with a hydrogen gas stream in plasma and reduced to form condensed solid phase of powder particles which grow then to further heat treatment. The potential utility of the powders for use in making anodes for electrolytic capacitors is described as to enhancement of specific surface area, particle diameter/bulk density, flow rate and compressibility. Schaefer in U.S. Pat. No. 2,766,112 (Oct. 9, 1956) describe hydrogen reduction in mixed tantalum and niobium chlorides.
Eaton et al. in U.S. Pat. No. 3,012,876 (Dec. 12, 1961) show a fluidized bed reactor process producing metals such as Nb, Ta, Mo, W, by hydrogen reduction of their oxyhalides in the presence of a fluidized bed of salt particles (alkaline earth metal salts) to act as substrates for the acquired metals from the hydrogen reduction (e.g. Ta, Nb).
Glaski et al. in U.S. Pat. No. 3,640,689 (Feb. 8, 1972) use chemical vapor deposition to establish a refractory metal interface layer between a chemical substrate and a bond layer face metal such as refractory metal carbides, the intermediate and face layers being deposited from intermediate chlorides (but with bromides and iodides mentioned as alternatives). Chemical vapor deposition to coat a metal surface is also disclosed by J. Eriksen in U.S. Pat. No. 7,479,301 (Jan. 20, 2008) with metal (e.g. Ta, Nb, Mo, W) halides reduced by hydrogen (with periodically interrupted flow of the hydrogen) in the process to establish smooth, nonporous surfaces, but with follow-up polishing with reactive halogen gas (fluorine, chlorine, bromine or iodine) or hydrogen-halides (HF, HCl, HBr, HI).
R. Winand in U.S. Pat. No. 4,830,665 (May 10, 1989) discloses production of alloyed and unalloyed reactive metals (Ti, Zr, Hf, Ta, Nb, Mo, W, U, Be, Cr) in a continuous reaction of metal halide in a liquid state with a gaseous reducing agent (e.g. hydrogen) at a temperature above melting point of the metal and continuous withdrawal of a solidified ingot.
Many other references are similar to the above mentioned ones dealing with overcoming difficulties of producing refractory metal products from crude or advanced original sources or recycling spent products to recapture them. Prominent among these is the task of recapture of valuable metals from superalloys and other sources as discussed above in connection with the Krynitz et al, Olbrich et al, Mishizawa et al., Stoller et al. and other patents and published patent applications. The metals industry also targets certain end uses in strategies for economically producing high purity metals of controlled properties. These usages include superalloys for aerospace products such as airfoils and turbine engine parts, cemented carbide tools or tungsten or molybdenum radiation targets. The sources of materials that can be used include superalloys or other refractory metals recovered from spent devices or other scrap or crude source materials, targeting particularly the most valuable metals such as rhenium, tantalum, niobium, tungsten, molybdenum It is also desirable in such production processes to minimize collateral impurities such as metallic impurities and interstitial elements (e.g. oxygen, nitrogen, hydrogen, carbon) that can affect electrical or mechanical properties of end products.